scholarly journals Void-closure behavior and a new void-evolution model for various stress states

2021 ◽  
Vol 55 (1) ◽  
pp. 105-113
Author(s):  
F. Chen ◽  
X. Zhao ◽  
H. Chen ◽  
J. Ren
Keyword(s):  
Evolution Model ◽  
Void Closure ◽  
Void Evolution ◽  
Stress States

Investigation on the void closure efficiency in cogging processes of the large ingot by using a 3-D void evolution model

2016 ◽  
Vol 237 ◽  
pp. 371-385 ◽  
Author(s):  
Chao Feng ◽  
Zhenshan Cui ◽  
Mingxiang Liu ◽  
Xiaoqing Shang ◽  
Dashan Sui ◽  
...  
Keyword(s):  
Evolution Model ◽  
Large Ingot ◽  
Void Closure ◽  
Void Evolution

Damage and fatigue analysis of AA7050-T7451 plate with cold expanded hole based on a micro-void evolution model

2019 ◽  
Vol 54 (2) ◽  
pp. 105-115
Author(s):  
Fengmei Xue ◽  
Fuguo Li ◽  
Xiaolei Cui
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Three Dimensional ◽  
Complex Stress ◽  
Evolution Model ◽  
Fatigue Properties ◽  
Strengthening Effect ◽  
Void Evolution ◽  
Cold Worked ◽  
Three Dimensional Finite Element

The ultimate tensile strength and fatigue life of plate with cold worked hole under high loading are always key designing parameters in engineering field. In this article, different cold expanded degrees (ranging from 1.69% to 11.11%) are applied to plate specimens with a central hole, made of 7050-T7451 aluminum alloy. The damage and fatigue properties are investigated by the three-dimensional finite element method with a user subroutine embedded into a void evolution model under complex stress states. The damage analysis indicates that plastic damage becomes critical when the cold expanded degree is larger than 7.14%, which does not suit for further service due to the loss of toughness. The cold expanded degree of 5.26% is identified as the best. It can be found that the fatigue life improves with the increased cold expanded degree. The small cold expanded degree leads to poor strengthening effect because of lacking sufficient residual stress, while large cold expanded degree makes micro-cracks emerge, which is beneficial to the increase in strengthening. All these results prove that the numerical analysis can accurately predict fatigue behavior of AA7050-T7451 plate based on our proposed approach, which is expected to be a powerful method in engineering field.

scholarly journals Influence of Mechanical Anisotropy on Micro-Voids and Ductile Fracture Onset and Evolution in High-Strength Low Alloyed Steels

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 224 ◽  
Author(s):  
Francesco Iob ◽  
Luca Cortese ◽  
Andrea Di Schino ◽  
Tommaso Coppola
Keyword(s):  
Large Diameter ◽  
High Strength ◽  
Tensile Tests ◽  
Mechanical Anisotropy ◽  
Anisotropic Behavior ◽  
Notched Specimens ◽  
Void Distribution ◽  
Void Evolution ◽  
Spiral Line ◽  
Stress States

In this paper results of a wide and innovative mechanical assessment, that was performedon large diameter spiral line pipes for gas transportation, are reported. The anisotropic materialhardening has been characterized by tensile (smooth and notched specimens), torsion, andcompression tests. Tests were performed in the pipe of the pipe with specimens machined alongseveral orientations, taking into account the pipe through thickness direction. The influence ofdifferent triaxiality stress states on anisotropic behavior of the material have also been analyzed bymeans of tensile tests on notched specimens. After the experiments, the material was assessed bymeasuring the void distribution on the material as is, and on many deformed and fracturedspecimens, including tensile tests at different triaxiality, and torsion tests. The results showed that insuch a class of materials, the experimental void fraction is fully negligible and not related to theapplied plastic strain, even at the fracture proximity. As a consequence it can be concluded that, theplastic softening hypothesis may be dropped and damage due to void evolution hypothesis is notadequate.

scholarly journals Global and High-Resolution Damage Quantification in Dual-Phase Steel Bending Samples with Varying Stress States

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 319 ◽  
Author(s):  
Rickmer Meya ◽  
Carl Kusche ◽  
Christian Löbbe ◽  
Talal Al-Samman ◽  
Sandra Korte-Kerzel ◽  
...  
Keyword(s):  
High Resolution ◽  
Volume Fraction ◽  
Density Measurement ◽  
Stress Triaxiality ◽  
Vital Role ◽  
Integral Approach ◽  
Large Area ◽  
State Dependent ◽  
Void Evolution ◽  
Stress States

In a variety of modern, multi-phase steels, damage evolves during plastic deformation in the form of the nucleation, growth and coalescence of voids in the microstructure. These microscopic sites play a vital role in the evolution of the materials’ mechanical properties, and therefore the later performance of bent products, even without having yet led to macroscopic cracking. However, the characterization and quantification of these diminutive sites is complex and time-consuming, especially when areas large enough to be statistically relevant for a complete bent product are considered. Here, we propose two possible solutions to this problem: an advanced, SEM-based method for high-resolution, large-area imaging, and an integral approach for calculating the overall void volume fraction by means of density measurement. These are applied for two bending processes, conventional air bending and radial stress superposed bending (RSS bending), to investigate and compare the strain- and stress-state dependent void evolution. RSS bending reduces the stress triaxiality during forming, which is found to diminish the overall formation of damage sites and their growth by the complimentary characterization approaches of high-resolution SEM and global density measurements.

Comparison of Substructures Between Uniaxial and Biaxial Deformation in 1100-0 Aluminum

1981 ◽  
Vol 39 ◽  
pp. 52-53
Author(s):  
D. L. Rohr ◽  
S. S. Hecker
Keyword(s):  
Plastic Strain ◽  
Cell Walls ◽  
Room Temperature ◽  
Mechanical Response ◽  
Biaxial Tension ◽  
Initial Deformation ◽  
Uniaxial Deformation ◽  
Biaxial Deformation ◽  
Stress States ◽  
Comprehensive Study

As part of a comprehensive study of microstructural and mechanical response of metals to uniaxial and biaxial deformations, the development of substructure in 1100 A1 has been studied over a range of plastic strain for two stress states.Specimens of 1100 aluminum annealed at 350 C were tested in uniaxial (UT) and balanced biaxial tension (BBT) at room temperature to different strain levels. The biaxial specimens were produced by the in-plane punch stretching technique. Areas of known strain levels were prepared for TEM by lapping followed by jet electropolishing. All specimens were examined in a JEOL 200B run at 150 and 200 kV within 24 to 36 hours after testing.The development of the substructure with deformation is shown in Fig. 1 for both stress states. Initial deformation produces dislocation tangles, which form cell walls by 10% uniaxial deformation, and start to recover to form subgrains by 25%. The results of several hundred measurements of cell/subgrain sizes by a linear intercept technique are presented in Table I.

Short Stress State Questionnaire

2015 ◽  
Vol 31 (1) ◽  
pp. 20-30 ◽  
Author(s):  
William S. Helton ◽  
Katharina Näswall
Keyword(s):  
Stress State ◽  
Factor Structure ◽  
Human Performance ◽  
Self Report ◽  
Confirmatory Factor ◽  
Stress States ◽  
Related Stress ◽  
Using Data ◽  
Task Conditions ◽  
Multiple Samples

Conscious appraisals of stress, or stress states, are an important aspect of human performance. This article presents evidence supporting the validity and measurement characteristics of a short multidimensional self-report measure of stress state, the Short Stress State Questionnaire (SSSQ; Helton, 2004 ). The SSSQ measures task engagement, distress, and worry. A confirmatory factor analysis of the SSSQ using data pooled from multiple samples suggests the SSSQ does have a three factor structure and post-task changes are not due to changes in factor structure, but to mean level changes (state changes). In addition, the SSSQ demonstrates sensitivity to task stressors in line with hypotheses. Different task conditions elicited unique patterns of stress state on the three factors of the SSSQ in line with prior predictions. The 24-item SSSQ is a valid measure of stress state which may be useful to researchers interested in conscious appraisals of task-related stress.

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